The phenomena classified as "cluster headaches" previously had no explanation in sight, that is until researchers at the Karolinska Institute in Sweden conducted an experiment with patients. The researchers retrieved 500 blood samples from patients who had cluster headaches and found two areas in their genes that could be the reasoning for their pain. The researchers in Sweden then collaborated with others in Britain to test another 850 patients, where another two genetic areas were found to have influence. Then with some more research from the Netherlands and Norway were compiled with the already found data and a few more areas were linked to the cluster headaches. The areas that are linked to cluster headaches genetically are: neuroinflammation, sleep-wake cycles, pain signaling, and migraines. Although there is now a base amount of information regarding the origins of this painful phenomena, there is still more research to be done; and the Karolinska Institute plans to do so with a large scale research plan involving both genetic samples and clinical data. Hope is in sight for those with painful headaches!